In wellbore completions, various completion devices can be used to block a flow of fluid for a variety of reasons. A packer, for example, has been used to isolate a region of an annulus between the exterior of a tube string and the radial extent or side of the wellbore. A challenge in isolating regions of the annulus arises when the diameter of the wellbore departs from the expected or nominal value, for example, where a wash-out has occurred. Wash-outs can increase the wellbore interior diameter to larger than the gauge size of the drill that created the wellbore. A variety of designs have been employed to account for wash-outs, thereby allowing the packer to seal regions regardless of whether a wash-out has occurred in that region. One such design employs a swellable elastomeric material. The swellable elastomeric material can absorb wellbore fluid to engage the inside diameter of the wellbore, despite any wash-out conditions that may exist.
When using swellable materials in completion devices, such as wellbore packers, however, it is important to ensure that the swellable materials do not prematurely swell. Wellbore packers that prematurely swell can engage the wellbore before the wellbore completion is completely deployed into the well. This can cause the wellbore packer to shear, tear, or otherwise sustain damage, which can undermine the integrity of a sealing engagement between the completion device and the wellbore. Furthermore, it is not always known exactly how long deployment of the wellbore completion will take, as unforeseen delays may arise. Thus, the swellable material can be exposed to the wellbore fluid for an extended period of time, which can cause premature swelling of the completion device, even in completion devices that include swell-delaying structures, leading to destruction during subsequent insertion. Therefore, what is needed is a completion device that enables the effective use of swellable materials without premature activation.